There exists numerous types of display card holders available for different purposes.
U.S. design patent Ser. No. 298,554 discloses a card holder made of a single transparent plastic sheet folded four times in order to provide a card display stand. Other examples of table card holders are disclosed in U.S. industrial design Ser. No. 325,401 and in U.S. Pat. No. 4,704,813.
Some other prior art references disclose display card holders which may be fixed to a shelf. Thus, U.S. design patent Ser. No. 314,017 discloses a card holder made of rigid material, which comprises a clip system attachable to a leg edge of a shelf. U.S. Pat. No. 1,417,325 discloses a ticket holder formed from a single piece of material having a U-shape, which can be inserted onto the edge of the shelf. The card is then maintained in front of the shelf by means of resilient clasps or fingers.
Other apparatus identified in the prior art concern magnet attaching means. See, for example, U.S. Pat. Nos. 4,287,676, 4,310,978 and 4,918,848.
None of the prior art card holders known to the Applicant are designed to be fixed under a metal shelf having an edge with a downwardly extending leg while allowing easy access to the shelf.